This invention relates to a linkage mechanism, and more particularly, to a linkage mechanism which, in combination with a spring, provides for the resisting of movement of an element associated with the linkage mechanism in one direction with a substantially constant force throughout the travel of such element.
In the design of, for example, a conventional governor linkage mechanism, such linkage mechanism is generally arranged so that a pedal associated therewith is depressed to acutate such linkage. The movement of the pedal is resisted by a spring, and as the pedal is further and further depressed, the spring provides a greater and greater resistance to further depression of the pedal. That is, the force required to depress the pedal a given distance at the end of its travel is much greater than the force required to depress the pedal a certain distance at the beginning of its travel. Such increase in force has been found to cause operator fatigue resulting in a less than maximum efficiency of operation of the vehicle with which the governor linkage is associated.
U.S. Pat. No. 3,466,943 and U.S. Pat. No. 3,495,476 disclose variable-ratio lever mechanisms. However, in each of these systems, the variable-ratio lever mechanism produces in an initial portion of a stroke a large output movement with a low output force, and in a final portion of the stroke a high output force.